Heads for dermatology treatment

ABSTRACT

Methods and apparatus for dermatology treatment are provided which involve the use of continuous wave (CW) radiation, preheating of the treatment volume, precooling, cooling during treatment and post-treatment cooling of the epidermis above the treatment volume, various beam focusing techniques to reduce scattering and/or other techniques for reducing the cost and/or increasing the efficacy of optical radiation for use in hair removal and other dermatological treatments. A number of embodiments are included for achieving the various objectives indicated above.

RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.11/437,434, filed May 19, 2006, entitled “Heads for DermatologyTreatment,” which is a continuation of U.S. application Ser. No.10/274,582, filed Oct. 21, 2002, now issued as U.S. Pat. No. 7,077,840,entitled “Heads for Dermatology Treatment,” which is a continuation ofU.S. application Ser. No. 09/634,981, filed Aug. 9, 2000, now issued asU.S. Pat. No. 6,511,475, entitled “Heads for Dermatology Treatment,”which is a continuation of U.S. application Ser. No. 09/078,055, filedMay 13, 1998, now issued as U.S. Pat. No. 6,273,884, entitled “Methodand Apparatus for Dermatology Treatment,” which claims the benefit ofU.S. Provisional Application Nos. 60/046,542 filed May 15, 1997 and60/077,726 filed Mar. 12, 1998. The entire contents of all above-listedapplications are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to apparatus for using optical radiation to treatdermatological problems and, more particularly, to heads for suchapparatus which heads provide an elongated focus area at a selecteddepth and/or selected preconditioning, for example heating and/orcooling, of a treatment area.

BACKGROUND OF THE INVENTION

Lasers, lamps, and other sources of electromagnetic radiation,particularly in the optical wavebands, are being increasingly utilizedfor various dermatological treatments and, in particular, for theremoval of unwanted hair, spider veins, leg veins, other veins or otherblood vessels which are visible through the patient's skin, lesions,port-wine stains, tattoos, and the like. In performing such treatments,it is desirable that the cost for the treatment be kept as low aspossible, consistent with achieving desired results, and that risk ofinjury to the patient be minimized.

Since continuous wave (CW) lasers and other CW radiation sources aretypically substantially less expensive than pulsed sources of comparablewavelength and energy, for cost reasons, it would be preferable to useCW sources rather than pulsed sources for such dermatologicaltreatments. However, in order to avoid injury to the patient, theduration of energy application to a given area of the patient's skinmust be controlled, this generally resulting in the more expensivepulsed light sources being used for the various dermatologicaltreatments. Further, since the only way to get radiation to areas wheretreatment is desired, which areas are normally in the dermis, is totransmit the radiation to such area through the overlying epidermis,some portion of incident radiation is absorbed in the epidermis creatingthe potential for damage thereto. This is a particular problem wheremelanin is being targeted in the dermis, as is for example the case forvarious hair removal treatments, since there is a substantialconcentration of melanin in the lower portion of the epidermis at thedermal/epidermal (DE) junction. Further, the deeper in the dermis thattreatment is desired, and/or the larger the element being treated, themore energy must be used, this generally involving the use of a morepowerful laser or other radiation source and/or operating such sourcefor longer time durations. This further increases the potential forepidermal damage.

Some attempts have been made in the past to scan a CW radiation source,such as the laser, over a treatment area, which has been done with theradiation source spaced from the skin in order to facilitate movement ofthe source. However, techniques currently utilized for protecting theepidermis frequently involve contact cooling of the epidermis and, forcertain treatments such as hair removal, performing the treatment withpressure applied to the patient's skin is also desirable. Irradiation byuse of a head in contact with the skin also permits more efficienttransfer of energy into the patient's skin, thereby reducing the size ofthe source required for a given treatment energy density and, therefore,reducing the cost of such source. This cost could be further reduced ifthe radiation source is not the only source being utilized to heat thearea under treatment.

Another problem in performing laser dermatology treatments, particularlywhen such treatment is to be performed over an area larger than theoptical aperture of the applicator being utilized, is to obtainsubstantially uniform irradiation over the area so that sufficientradiation is applied to all portions of the area to achieve the desiredtreatment, while no portion of the area has so much radiation appliedthereto as to cause thermal damage to the skin. Such uniform irradiationis very difficult with a pulsed source which typically utilize acircular aperture. Typically, the procedure followed is to irradiate aspot with a given pulse and to then reposition the head to an adjacentspot for irradiation. If the spots do not overlap, there will beportions of the area under treatment which do not receive radiation and,unfortunately, the radiation output is frequently not uniform over theentire optical aperture, being greater near the center, and less at theedges. Therefore, there is generally some overlap between adjacentspots. However, this results in some portions of the area undertreatment receiving at least a double dose of radiation, which poses apotential danger of thermal damage in these overlap areas. Substantiallyuniform irradiation of a treatment area is therefore virtuallyimpossible with a pulsed radiation source utilizing existing techniques.

Another problem which increases the energy required from the radiationsource utilized is that, for existing systems, heating of the target toachieve the desired therapeutic effect is accomplished solely byradiation from the radiation source. If the temperature of the targetcould be increased by some type of preheating of the target volume, theamount of energy required from the radiation source to complete the jobwould be substantially reduced. However, such preheating must beachieved in a way such that the cost of such preheating is not greaterthan the savings achieved by reduced requirements on the radiationsource.

Similarly, in order to protect the epidermis, many procedures requirethat the epidermis be cooled, preferably to the DE junction, to at leasta selected temperature, for example 10° C., 0° C., or even slightlylower, before radiation is applied. If contact cooling starts when thehead is over the target area, this means that there is some delay,perhaps half a second to a second, between the time the head is appliedto the patient's skin and the time the radiation source is fired. WithCW, such a delay once the radiation source is over the target area isdifficult to achieve and it is therefore preferable that precooling ofthe epidermis occur for the target area before the radiation source isthereover. An ideal procedure would be to preheat the skin down to thetarget depth and then to precool to the DE junction, leaving the targetdepth preheated. Mechanisms in general, and heads in particular, forachieving such precooling and/or preheating followed by precooling havenot heretofore existed.

It is also desirable to be able to focus the optical radiation atsubstantially the target depth. While heads have heretofore existedwhich are capable of achieving such a focus on a given spot, fasteroperation, particularly when operating in CW mode, although also whenoperating in pulse mode under some circumstances, can be achieved ifthere is a line focus at the target depth rather than a point focus.Mechanisms for achieving such a line focus have also not heretoforeexisted.

A need therefore exists for improved apparatus for utilizing opticalradiation to treat various dermatological conditions, and in particular,improved heads for use in such apparatus which facilitate preheatingand/or precooling of the target area, particularly when operating in CWmode, but also when operating in other modes, and which also facilitateachieving of a line focus for the radiation at a selected target depthfor enhanced, and in particular, more rapid treatment.

SUMMARY OF THE INVENTION

In accordance with the above, this invention provides various heads foruse in apparatus for effecting a selected dermatologic treatment in anarea of a patient's skin. For some embodiments, the head includes ablock formed of a material having good thermal transfer properties, aplurality of first optical waveguide elements and a plurality of secondoptical waveguide elements extending through the block, the first andsecond optical waveguide elements being angled at first and secondangles respectively, which angles are selected so that light passingthrough the first and second optical waveguide elements converge at aselected depth. The optical waveguide elements have radiation appliedthereto which is appropriate for the selected dermatologic treatment.The selected depth is in the area under treatment at which thedermatologic treatment is to occur. For some embodiments, a recess isformed in a surface of the head in contact with the patient's skin, therecess being at the distal end of the optical waveguide elements, andthe selected depth is at a selected location in the recess. For theseembodiments, a means is provided for moving skin in the area undertreatment into said recess as said recess passes thereover. This meansmay, for example, include a source of negative pressure connected to therecess. For preferred embodiments, the block also has a skin contactingsurface which retroreflects radiation leaving the patient's skin. Amechanism may also be provided for controlling the temperature of eitherthe entire block or selected portions thereof.

For other embodiments, the head includes an astigmatic lens having anelongated outer surface, one side of said surface contacting thepatient's skin in the area to be treated along an elongated line. Amechanism is provided which delivers light of a wavelength suitable forthe dermatologic procedure to the lens on a side thereof other than theside contacting the patient's skin, the lens focusing light deliveredthereto to a selected depth in the patient's skin. The lens may be acylindrical lens with a diameter such that light delivered thereto isfocused to the selected depth, and may be mounted to be eitherstationary or rotating as the head is moved over a treatment area. Forsome embodiments, the lens is treated so as to normally have totalinternal reflection, the total internal reflection being broken at asurface of the lens in contact with the patient's skin. To achieve thedesired focus, the radius of curvature of the cylindrical lens for someembodiments is less than or equal 10 mm. For some embodiments, theselected depth is that for a portion of a hair follicle responsible atleast in part for hair growth, for example, the hair bulge or the hairbulb. The selected depth may, for example, be 1 mm to 5 mm.

The mechanism for delivering light to the lens may deliver light along aline substantially parallel to the elongated line contacting thepatient's skin surface and/or may cause light to be delivered to thelens at a variety of angles. A cooling mechanism may also be availablefor the patient's skin before the lens makes contact with the skinand/or while the lens is in such contact, the cooling mechanism for someembodiments, including a mechanism for cooling the lens. For someembodiments, the lens focuses light at said selected depth to anastigmatic focus area having a long dimension substantially parallel tothe elongated line of lens contact with the skin. Finally, for someembodiments, the mechanism delivering light to the lens scans along thelens in its elongated direction, the scanning being at a selected rate.

More generally, the invention includes a focusing element having a lightreceiving region, a light delivery region which is adapted to be incontact with the patient's skin and a region which focuses lightentering at said receiving region, the focus, when such element is incontact with the patient's skin being to an elongated astigmatic focusarea at a selected skin depth. A mechanism is included which deliverslight of a wavelength suitable for the dermatologic procedure to thelight receiving region. The selected depth for some embodiments is thedepth for a portion of a hair follicle responsible at least in part forhair growth, for example the hair bulge and/or hair bulb, and may beapproximately 1 mm to 5 mm into the skin. A cooling mechanism for thepatient's skin may also be provided, which mechanism is operated beforethe element makes contact with the skin and/or while the element is incontact therewith.

In accordance with still another embodiment of the invention, the headincludes an optically transparent channel for delivering opticalradiation of a wavelength appropriate for effecting the treatment in thearea, a head portion of a thermally conductive material mounted relativeto the channel so that it moves over each segment to be treated of sucharea before the channel, and a thermal component which controls thetemperature of the head portion, and thus of each skin segment prior totreatment. In particular, the component may cool the portion, and thuseach skin segment prior to treatment and/or the component may heat theportion, and thus heat each segment prior to treatment. The head mayinclude a block formed of a material having good heat transferproperties, the block being adapted to move over the area duringtreatment, the channel being formed through the block and the portionbeing a portion of the block which is forward of the channel as theblock is moved over the area. The head portion forward of the channelmay be divided into a first thermally conductive portion which is heatedand a second thermally conductive portion which is cooled, whichportions are thermally insulated from each other, the first portionheating the patient's skin to the depth where treatment is to beperformed and the second portion then cooling the patient's epidermisprior to irradiation. The head may also include a portion of a thermallyconductive material mounted relative to the channel so that it movesover each segment to be treated of the area after the channel; and athermal component which cools such rear head portion, and thus each skinsegment after treatment.

While for preferred embodiments, preheating of the skin in the treatmentarea is accomplished in conjunction with the use of CW radiation andmovement of the head over the treatment area, this is not a limitationon the invention, and preheating of the treatment area is alsoadvantageous when employed with a pulsed radiation source. For suchapplications, preheating could be achieved by heating the waveguide orthe portion of the head in contact with the segment under treatmentprior to treatment to heat the skin down to at least to the depth wheretreatment is desired to a temperature which temperature is below that atwhich thermal damage occurs; and to then cool the surface in contactwith the epidermis to cool the epidermis before irradiation begins. Thisresults in the area under treatment having an elevated temperature whenirradiation begins, thereby reducing the energy required from theradiation source. Alternatively, a low energy radiation source, whichcan be either the same or different than that used for treatment, can beused to perform the preheating operation.

The foregoing and other objects, features and advantages of theinvention will be apparent in the following more particular descriptionof preferred embodiments of the invention as illustrated in theaccompanying drawings.

IN THE DRAWINGS

FIG. 1 is a semi-schematic perspective view of apparatus suitable forpracticing the teachings of this invention;

FIG. 2 is a sectional view of a head useful for practicing the teachingsof this invention in accordance with a first embodiment;

FIG. 3 is a sectional view of a head suitable for practicing theteachings of this invention in accordance with a second embodiment;

FIG. 4 is a sectional view of a head suitable for practicing theteachings of this invention in accordance with a third embodiment;

FIG. 5 is a perspective sectional view of a head suitable for practicingthe teachings of this invention in accordance with a fourth embodiment;

FIGS. 6 a-6 b illustrate two embodiments of astigmatic transparentchannel suitable for use in a head of the various embodiments to deliverradiant energy;

FIG. 7 is a side view of a head in use which is suitable for practicingthe teachings of this invention in accordance with a fifth embodiment;

FIG. 8 is a side sectional view of a head suitable for practicing theteachings of this invention in accordance with a sixth embodiment;

FIG. 9 is a top perspective view of a head suitable for practicing theteachings of this invention in accordance with a seventh embodiment;

FIGS. 10 a and 10 b are a side sectional view and a front view,respectively, of a head suitable for practicing the teachings of thisinvention in accordance with an eighth embodiment;

FIGS. 11 a, 11 b and 11 c are a side view, a front view when not incontact with a patient's skin, and a front view in contact with thepatient's skin, for a head suitable for practicing the teachings of thisinvention in accordance with a ninth embodiment;

FIGS. 12 a and 12 b are perspective views of portions of a headillustrating various techniques for scanning a radiation source acrossan astigmatic radiation delivery channel;

FIG. 13 is a side sectional view of a head suitable for practicing oneaspect of the invention in accordance with a tenth embodiment;

FIG. 14 is a graph illustrating the relationship between temperature atthe basal layer and scanning velocity when practicing the teachings ofthis invention; and

FIG. 15 is a chart illustrating the relationship between scanningvelocity of the head and the maximum temperature of a hair bulb locatedat a selected depth.

FIG. 16 is a chart illustrating the relationship between power per unitlength and maximum temperature of the hair bulb at a selected depth fortwo different sizes of hair bulb.

DETAILED DESCRIPTION

FIG. 1 illustrates a general system suitable for practicing theteachings of this invention. In FIG. 1, an area 10 of a patient's skinis shown on which a selected dermatologic treatment is to be performed.As indicated earlier, the treatment may be for removal of unwanted hair,tattoos, port wine stains, spider veins or other vascular lesions, etc.The patient's skin has an epidermal layer 12 and a dermal layer 14, witha dermal-epidermal (D/E) junction or basal layer 16 therebetween. Whilesome dermatologic treatments may involve heating the epidermis 17, suchas for example skin resurfacing, most dermatologic treatments whichinvolve the use of optical radiation treat a condition located at aselected volume (sometimes hereinafter referred to as the target volumeor target) within dermal layer 14. For example, when the dermatologicaltreatment is hair removal, it may be desired to heat and destroy thebulb 18 of a hair follicle 20. While epidermis 12 might for example be0.01 cm deep, bulb 18 might, for example, be 3.0 to 5.0 millimeters intothe skin. Utilizing the teachings of this invention, a plurality of hairfollicles 20 may be simultaneously heated and destroyed.

The apparatus of this invention includes an applicator 22 which may bemechanically driven, but which, for purposes of the followingdiscussion, will be assumed to be hand operated (i.e., translated overthe skin surface by hand). Applicator 22 includes a head 24 in contactwith the patient's skin in the treatment area and a handle 26 which maybe grasped by an operator to move head 24 in for example direction 28across the patient's skin while preferably maintaining contact betweenhead 24 and the patient's skin. Such contact should be under sufficientpressure between the surface of the head and the skin surface so as to,for preferred embodiments, assure good thermal and optical contacttherebetween. Such pressure can be achieved by pressing the head againstthe skin, by using negative pressure to press the skin against the heador some combination of the two.

For some embodiments of the invention, a source of optical radiation 30is connected to a light pipe 32, which for the embodiment of FIG. 1 isshown as extending through handle 26, but may otherwise be connected tohead 24, to selectively provide optical radiation to the head, radiationbeing applied through the head, in a manner to be discussed later, tothe patient's skin. Source 30 may be a coherent light source such as aruby, alexandrite, or other solid laser source, a gaseous laser source,or a diode laser source, or may be an incoherent light source such as aflashlamp, fluorescent lamp, halogen lamp, or other suitable lamp.Depending on the desired treatment, the radiant energy may be at asingle wavelength, with incoherent light sources being filtered toprovide the desired wavelength, or over a selected band of wavelengths.In the following discussion, when it is indicated that radiation isbeing applied at a selected wavelength, this will mean either a singlewavelength or a wavelength band, as appropriate. Source 30 in accordancewith preferred embodiments of this invention is also a CW source which,for purposes of this invention shall be defined as either a light sourcewhich is producing radiation continuously or a pulsed source with a highrepetition rate/frequency, and in particular which has a delay betweenpulses which is less than the dwell time of the head on a given segment.CW radiation is defined as radiation from either such source.

While in FIG. 1 source 30 is shown as external to head 24, for someembodiments of the invention which involve the use of a diode laser,diode laser bar or other sufficiently compact radiation source, thesource may be located in head 24, with wires for controlling andenergizing the source being connected through handle 26 or otherwise tothe head. Controls 34 are also provided which receive certaininformation from head 24 over lines 36, for example information relatingto rate of movement of head 24 over the patient's skin, or temperatureof the epidermis and which may send control signals to the head overlines 38 as required. Lines 36 and 38 may be part of a cable which isalso connected to head 24 through handle 26 or may be otherwiseconnected to the head. Controls 34 may also generate outputs to controlthe operation of source 30 and may receive information from the source.Controls 34 may also control selected output devices 40, for example abuzzer, light, vibrator or other feedback control to an operator or,depending on application, may be of other types known in the art.

Before discussing specific embodiments for head 24 and the manner inwhich the system of FIG. 1 may be utilized to treat variousdermatological conditions in accordance with such embodiments, it shouldbe appreciated that maintaining head 24 in good thermal and opticalcontact with the surface of the patient's skin during treatment whileapplying CW radiation from source 30, whether located external to head24 as shown in FIG. 1 or within the head, offers a number of significantadvantages when performing various dermatological treatments. First, asindicated earlier, for the same radiation source operating at comparableenergy levels, a CW source is almost always substantially less expensivethan a comparable pulsed source. Therefore, the ability to use a CWsource results in a significant reduction in system cost. Second, ifhead 24 is moved across the surface of the patient's skin at asubstantially uniform rate, the radiation applied to the patient's skinat each point along the path of travel of head 24 is substantially thesame, something which, as indicated above, cannot easily be achievedwith a pulsed radiation source. The head being in good optical contactwith the patient's skin improves the efficiencies of energy transferinto the skin, further reducing the size and cost of the required energysource. Further, the head 24 being in good thermal contact with thepatient's skin permits the head to be used to heat the volume in thepatient's dermis at which treatment is to occur, for example the area ofbulb 18 for a hair removal procedure, so as to reduce the amount ofenergy required from the radiation source in order to perform thedesired procedure at this volume, thus further reducing the cost of suchsource. Good thermal contact also permits the head to be utilized tocool the patient's epidermis 12 before irradiation, during irradiation,and after irradiation, to protect the epidermis from thermal damage.Applying pressure to head 24 as it is moved across the surface oftreatment area 10 also stretches the skin in the treatment area whichcan provide a number of advantages, including reducing the physicaldistance between the head and the target volume, reducing thecoefficient of scattering in the skin so that more of the appliedradiation reaches the target volume and, for hair removal, flatteningthe hair follicle so as to increase the area of the follicle exposed toradiation. All of these effects reduce the amount of radiation requiredfrom the source, thereby further reducing the cost of the system.Various techniques are available for measuring/detecting good thermalcontact between a head and the patient's skin including the temperatureprofile detecting technique of copending application Ser. No. 60/077,726filed Mar. 12, 1998, which application is incorporated herein byreference. FIG. 2 illustrates one exemplary embodiment for a hand piece24A suitable for use in practicing the teachings of this invention. Inthe discussion of this embodiment, and in the embodiments to follow, thesame reference numerals will be used for common elements. Lettersuffixes will be used for elements which are substantially the same, butdiffer in some particulars. Thus, the letters 24A, 24B, etc. are usedfor the various embodiments of handpiece 24.

Handpiece 24A has three sections, an optical channel 50 which is shownin FIG. 2 as a waveguide, a leading section 52 which passes overtreatment area 10 before waveguide 50 and a trailing section 54 whichpasses over the treatment area after waveguide 50. Optical radiation isapplied to waveguide 50 through optical fibers 32 (or fiber bundle) orother suitable optical transmission components or, as will be discussedlater, laser diodes or other suitable components may be in contact withwaveguide 50. Waveguide 50 may also be replaced with a lens or othersuitable focusing or non-focusing optical transmission component (awaveguide, lens or other suitable focusing or non-focusing opticaltransmission component sometimes being collectively referred tohereinafter as an “optical channel”), which optical transmissioncomponent receives radiation from the radiation source utilized througha suitable optical transmission path. Other arrangements for gettingradiation to optical channel 50 can also be employed.

Sections 52 and 54 are each formed of a metal or other material havinggood thermal conduction properties. Sections 52 and 54 may be formed asa single block of a single material, with optical channel 50 beingformed in the block, or, where sections 52 and 54 are to have differenttemperature profiles, the sections may, as will be discussed later, betwo separate sections of the same or different materials securedtogether with a layer of thermal insulation therebetween. In FIG. 2, athermal component 56 a, 56 b, 56 c is shown in contact with section 52,waveguide 50, and section 54, respectively. For a preferred embodiment,each of the thermal components 56 is a thermoelectric element such as aPeltier effect device; however, other mechanisms for controllingtemperature known in the art, including flowing water, and flowing gasor spray at a desired temperature may be utilized for thermal components56. In applications where sections 52 and 54 have the same temperatureprofile, the same thermal component may be used to control thetemperature of both sections; however, particularly if thermoelectriccomponents are used, it is preferable that a number of these componentsbe utilized, distributed over sections 52 and 54 so as to achieve asubstantially uniform temperature distribution in these sections.

FIG. 3 shows a head 24B which is substantially the same as the head 24Ashown in FIG. 2 except that, in addition to sections 52 and 54, head 24Balso has a section 58, ahead of section 52, with a thermal insulationlayer 60 being provided between sections 52 and 58. Section 58 is alsoformed of a metal or other material having good thermal conductioncharacteristics and a thermal element 56 d, for example one or morethermoelectric or thermal resistance elements, is provided in thermalcontact with section 58. As will be discussed shortly, section 58 isintended to have a different temperature profile than section 52.

For the embodiment of FIG. 2, section 52 may be utilized to eitherpre-heat or pre-cool the patient's skin in the treatment area. For ahead 24 moving at a velocity V in direction 28, V sometimes also beingreferred to as the “scanning velocity”, and for a length of section 52in the direction of movement 28 equal to L₁, the time T₁ during whichsection 52 is over a segment of the patient's skin prior to treatment,and thus the time of pre-heating

$T_{1} = \frac{L_{1}}{V}$

or pre-cooling, is roughly directly proportional to L₁ and inverselyproportional to V. Thus,

$T_{z} = \frac{z^{2}}{4\alpha}$

Since the time it takes for a temperature wave to penetrate to a depth zin the skin is, where α is the skin thermal-diffusion coefficient(α≈1.5·10⁻³ cm²/s). Therefore if these two times (T₁ and T₂) are roughlyequal, then:

$z = \frac{\sqrt{4{\alpha \cdot L_{1}}}}{V}$

and the desired thermal effect will reach a desired depth z during theperiod that section 52 overlies the skin segment. Thus, L₁ and V can beselected so as to achieve the desired thermal effect at a desired depthin the skin prior to irradiation. Since, as will be discussed shortly, Vis also a factor in determining the duration of irradiation forachieving the desired therapeutic effect, L₁ may be the prime factor indetermining the depth for the desired thermal effect. For pre-heating,the depth z is the depth of the volume at which treatment is desired.For example, referring to FIG. 1, z might be the depth of bulb 18 of ahair follicle where the treatment is hair removal. For pre-cooling, itis generally desired to cool the entire epidermis 12 to DE junction 16.It is generally undesirable to cool significantly below the DE junctionsince this may interfere with treatment by having some cooling effect onthe treatment or target volume. Depending on the function section 52 isto perform and the scanning rate V, L₁ is selected so as to achieve thedesired thermal effect to the desired depth z.

FIG. 3 differs from FIG. 2 in that there are two pre-temperaturemodifying sections 52 and 58. With this arrangement, section 58 istypically heated to pre-heat to the depth z_(c) of the target volume.Section 52 is cooled and is intended to subsequently cool the epidermisto roughly DE junction 16. Since heating performed by section 58 is to agreater depth than the cooling performed by section 52, L₄ is shown asbeing greater than L₁ in FIG. 3. The combination of sections 52 and 58permits the target to be heated and remain heated prior to irradiationwhile the epidermis is protected against thermal damage by being cooledprior to irradiation.

The temperature profile at the depth z is a function of the initialtemperature of the skin and of the temperature of the section 52, 58 forhead 24B. The length of the segment L₁ and scanning velocity V are alsofactors in determining the final temperature at depth z. An estimate ofskin temperature at depth z can be made using Thomson's equation asfollows:

${T\left( {z,V,L_{1}} \right)} = {2 \cdot \frac{T_{0} - T_{1}}{\sqrt{\pi}} \cdot {\int_{0}^{\frac{z}{2\sqrt{\frac{\alpha \; L_{1}}{V}}}}{^{- \xi^{2}}\ {{\xi\_ T}_{1}}}}}$

where T₀ is the initial temperature of the skin, T₁ is the initialtemperature of the segment which is assumed for purposes of the equationto be segment 52. For scanning velocities in the range of approximately0.05 to 10 cm/s, and length L of approximately 0.125 cm, desiredpre-heating to a temperature in the range of +40° C. to +60° C. orpre-cooling of −30° C. to +20° C. can be achieved. Typically, theepidermis would be cooled to the DE junction to a temperature in the −5°C. to 0° C. range. Scanning velocities up to 10 cm/s should beachievable with contact scanning, but scanning velocities in excess of10 cm/s may be more difficult to achieve.

The embodiment of FIG. 3 complicates the determination of appropriateparameters since scanning velocity V, which is the same for allsections, must be selected so that pre-heating can be achieved to adesired depth with an L₄ of reasonable size, pre-cooling to the DEjunction can be achieved with an L₁ of reasonable size, and the desiredtherapeutic effect can be achieved, using the radiation source with agiven fluence and for a reasonably achievable value of L₂. This issomewhat complicated by the fact that in order to heat deep layers ofthe skin (i.e., greater than 3 mm) the scanning velocity should notexceed approximately 0.1 to 0.2 cm/s, while for heating of subsurfacelayers of the skin (less than 1 mm) the scanning velocity can be up to 2cm/s. This assumes an L₄ of approximately 5 cm or less.

Radiation passing through waveguide or other optically transparentcomponent 50 is directed through the epidermis, which has preferablybeen pre-cooled to the target, which may have been pre-heated, in orderto achieve the desired therapeutic effect. In determining the timeduring which the target is irradiated, account must be taken of the factthat, due to scattering in the patient's skin, the beam width at thetarget can be greater than L₂, the width of radiation at the skinsurface, by a value Δ. Value L₂+Δ can be minimized by focusing of thebeam. Thus, the exposure time T₂ of the target to CW radiation is givenas,

$T_{2} = \frac{L_{2} + \Delta}{V}$

The target has a thermal relaxation time which is generally a functionof its size and of its shape. It is generally desirable that the time T₂be roughly equal to the thermal relaxation time of the target, assumingdestruction of the target is the desired therapeutic effect, since thisresults in maximum heating of the target with minimal heating ofsurrounding tissue. In applications such as hair removal, where it hasbeen found that some damage to a small layer of tissue surrounding thefollicle facilitates permanent, or at least more permanent, hairremoval, it may be desirable for the time T₂ to be slightly greater thanthe thermal relaxation time of the target. In any event, for a targethaving a size or diameter d, the critical velocity at which dwell timeon the target is roughly equal to its thermal relaxation time is givenby,

$V_{c} = \frac{{g\left( {L_{2} + \Delta} \right)}\alpha}{d^{2}}$

where g is shape factor (g=8, 16 and 24 for stratified, cylindrical andspherical targets, respectively). Thus, where bulb 18 of a follicle isthe target, g would be approximately 24. Assuming a maximum scanningvelocity of 10 cm/s, and also assuming a depth z≈3 mm and L₂+Δ of about3 mm, equation (6) suggests that the process works best for stratifiedtargets like fat layer with a thickness greater than 190 μm, cylindricaltargets like a blood vessel with a diameter greater than 270 μm, andspherical targets like a hair bulb with a diameter greater than 320 μm.However, since, as discussed earlier, lower velocities would typicallybe employed in order to achieve pre-heating and/or pre-cooling forsection 52, 58, significantly larger minimum target volumes are requiredfor the various shapes in a practical system. However, since V_(c) isonly a guide, and times less than or greater than thermal relaxationtime of the target may be appropriate in some treatments, treatabletarget sizes will also vary. Effective pre-heating of the target mayalso reduce the required dwell time to achieve a desired therapeuticeffect.

Another concern when employing the teachings of this invention fordermatologic treatment is that the temperature rise at the target besufficient to achieve the desired effect. Where the treatment beingperformed is hair removal utilizing techniques similar to thosedescribed in U.S. Pat. No. 5,735,844 issued Apr. 7, 1998, it isnecessary to heat the hair bulb to a temperature of approximately 65° C.to 75° C. The maximum temperature of a hair bulb undergoing irradiationis given by the following equation,

$T_{m} = {{\frac{6{\tau (d)}\left( {1 - {\exp \left( {- \frac{a}{{\tau (d)} \cdot V}} \right)}} \right)}{c \cdot \rho \cdot d}{{k(\lambda)} \cdot {\psi \left( {z,\lambda} \right)} \cdot P}} + T_{0}}$

where, z is the depth of the bulb 18 in the skin T₀ is the initialtemperature of the bulb before irradiation a is the size of theirradiate zone inside the skin along the scanning direction at the depthz (as previously indicated a=L₂+Δ) c and ρ are the heat-capacity anddensity of the bulb respectively k(λ) is the absorbing ability of thehair bulb and shaft defined by a concentration and a type of melanin,and depends on wavelength (is greater for dark hair and less for lighterhair) ψ(z, λ) is the radiance inside the skin at the depth z, caused bya light flux of unit power per length. It depends on both scattering andabsorption inside the skin P is the power per unit length (i.e., equalto the total power applied to the skin surface per width of the lightbeam in the direction perpendicular to the direction of scanning. P isin units of W/cm. τ(d)=d²/gα is a period of thermal relaxation, where dis a diameter of the bulb, g is as previously indicated equal to 24 fora hair bulb, and α is the thermal diffusion coefficient of the tissuearound the bulb.

For the destruction of a hair bulb, λ is in a range of 600-1200 nm andis preferably in a range of 670-1100 nm. In this range, k(λ) varies from1-0.1 and decreases with increasing wavelength. ψ(z, λ) in this rangeincreases with wavelength because of the weakening of the skinscattering properties and decreases with depth. At a depth of 3-5 mmwhere a hair bulb in its anagen stage is typically locate, this value,which is sometimes referred to as radiance attenuation, is in the rangeof 0.1-0.5. This value may be significantly increased where focusingtechniques to be described later are used. With focusing, the reflectioncoefficient of light from the skin can be 20%-70%. Further, reflectionof light scattered from the skin back into it by various means to bedescribed increases the radiance in the zone of the hair bulge or in ahair bulb 1.2-2.5 times. Thus, the devices of this invention can allowψ(z, λ) to be increased to 0.5-1.

From the above, it can be seen that, once the geometry of the systemshas been selected, the temperature at the bulb is directly proportionalto the applied power P and is

$T_{m} = {\frac{6 \cdot P \cdot d \cdot k \cdot \psi}{g \cdot \alpha \cdot c \cdot \rho \cdot a} + T_{0}}$

inversely proportional to the velocity V in a more complex way. FIG. 15illustrates the dependence of maximum temperature at a hair bulb onscanning velocity V for typical parameters. The curve of FIG. 15 iscalculated assuming a=0.3 cm, k=0.5, ψ=0.5, P=40 W/cm², d=0.03 cm. FromFIG. 15, it is seen that at low scanning velocities, T_(m) does notdepend on scanning velocity and is equal to

$V_{m} = \frac{g \cdot a \cdot \alpha}{3 \cdot d^{2}}$

When the scanning velocity exceedstemperature T_(m) starts to decrease.

When V is less than V_(m), the average temperature of the hair bulb doesnot change with changing velocity, but selectivity of thermal damagedecreases. Thus, by decreasing the velocity of scanning, it is possibleto increase the diameter of the zone of thermal damage around the hairbulb. Maximum scanning velocity depends on the hair bulb dimension anddecreases as the size of the follicle increases.

FIG. 16 shows the dependence of T_(m) for a hair bulb on the power perunit length P. For a treatment period of less than 1 second,denaturization of protein structures is observed at temperatureexceeding 65° C. From FIG. 16, it is seen that maximum temperature T_(m)at a hair bulb is also a function of the power P per unit length. For atreatment of less than 1 second, denaturization of protein structures isobserved to occur at temperatures exceeding 65° C. FIG. 16 alsoillustrates that the power required to cause thermal damage in a hairbulb is inversely proportional to the size of the hair bulb (i.e.,thermal damage is caused at a lower power for a large bulb than for asmall bulb).

Thus, for hair removal, and regardless of the embodiment utilized, thefollowing parameters would apply:

1. Wavelength: 600-1200 nm;

2. average power per length unit: 5-150 W/cm;

3. width of beam along direction of scanning: 0.05-5 mm;

4. scanning velocity: 0.01-10 cm/s;

5. temperature of cooling: −20° C.-+30° C.

For preferred embodiments, optically transparent section 50 is alsocooled by thermal element(s) 56 b so as to prevent, or at least limit,heating of epidermis 12 in the treatment area during irradiation. Thiscooling effect is also a function of the scanning velocity and isparticularly critical where irradiation used is of a wavelength whichpreferentially targets melanin, as is for example the case for certainhair removal treatments. Since there is a high concentration of melaninat DE junction 16, it is desirable that V be slow enough so as to permitheat produced at the DE junction to be removed through the cooledwaveguide or other cooled optically transparent element 50. The maximumscanning velocity at which the cooling effect becomes noticeable for agiven depth z is given by,

$V_{\max} = \frac{4 \cdot L_{2} \cdot \alpha}{z^{2}}$

Where epidermis 12 to be cooled has a thickness of approximately 100 μmand the length L₂ is approximately 1 mm, V_(max)=6 cm/s.

Further, as indicated earlier, the pressure applied to the skin by head24 in general, and by the skin-contacting surface of element 50 inparticular, has a number of advantages, including improving the opticaltransmission (i.e., reducing scattering) for radiation passing throughthe skin. The head moving in the direction 28 over area 10 of the skinalso stretches the skin in the direction of scanning resulting in anadditional increase in skin transmission and thus the depth ofelectromagnetic wave penetration into the skin. Further, when the targetis for example a hair follicle, the stretching of the skin turns thefollicle to cause the radiation to impinge on a larger portion of thefollicle and brings the follicle nearer to the skin surface.

Section 54 continues to cool the epidermis after irradiation to furtherguard against potential thermal damage to the skin. Unlike lengths L₁,L₂ and L₄ which are fairly critical, the length L₃ is not critical. Thepurpose of this section is to assure that the epidermis is notoverheated and, if the prior sections are effective in keeping theepidermis temperature down, section 54 may not be required.

Since it is generally desirable to decrease the time element 50 is overthe target, it is generally desirable that L₂ be kept small. However, inorder to achieve more rapid treatment, a significant beam aperture isdesirable. This suggests that the dimension of the beam perpendicular tothe direction of movement should be relatively large, resulting in anaperture for the skin contacting surface of element 50 which has anastigmatic shape, which shape may also be asymmetric. FIG. 6 illustratestwo such shapes, namely an oval 66 (FIG. 6 a), and a series of adjacentlight pipes 76 a, 76 b as shown in FIG. 6 b, the light pipes of FIG. 6 bbeing discussed in greater detail in conjunction with FIG. 4. Theseshapes are just examples of astigmatic shapes for an optical aperture,and many other astigmatic shapes are within the contemplation of theinvention.

Further, in order to deliver the radiation to a significant depth (i.e.,greater than 1 mm) efficiently, large diameter beams are generallyrequired to overcome the effect of scattering. With astigmatic beams ofthe type shown in FIG. 6, it is therefore desirable that focusing of thebeam in a direction perpendicular to the direction of scanning be used.One way of achieving this is through use of a cylindrical lens 70 suchas is shown in FIG. 9 which lens has a small radius of curvature (forexample less than 10 mm). However, such focusing can perhaps be betterachieved through use of a head 24C such as that shown in FIG. 4. Thishead has a section 52 which functions in the same way as section 52 ofhead 24A to pre-cool or pre-heat the area under treatment. Section 52 isseparated from a section 72 of the head by a layer of thermal insulationmaterial 74. Section 72 is also formed of a metal or other materialhaving good thermal conduction properties. Two rows of micro-opticelements 76 a and 76 b are provided which extend through section 72 andare angled so that their focuses are combined along a common linelocated at the target depth. Microlenses may be included at the distalends of elements 76 to enhance focusing. This technique allows the beamsto be targeted into the skin at angles greater and can be achieved usingoptical systems and more effectively compensates for the scattering ofradiation in the skin. Section 72 would be cooled, preferably by anumber of thermoelectrical elements 56 b, so as to provide bothpre-cooling of the epidermis prior to irradiation, cooling of theepidermis during irradiation, and post-cooling of the epidermis. Section72 can thus perform the cooling functions of sections 50, 52 and 54 offor example the embodiment of FIG. 2. Thus, for this embodiment of theinvention, section 52 can be used as a pre-heater or can be eliminated.

FIG. 4 also illustrates some additional features. First, it shows anoptical channel 78 which can be connected to a suitable detector incontrols 34 for detecting the scan velocity of head 28. Other techniqueswhich will be discussed in conjunction with FIG. 10 may also be used forperforming this function. Detecting scan velocity permits controls 35 tooperate output 40 if the scan velocity is detected to be outside ofdesired ranges so as to alert the operator so that the rate may beincreased or decreased as appropriate. For example, the output may be ared or a green light on some portion of applicator 22 or a consoleassociated therewith, might be a voice, or buzzer or other audio alertto the operator, might be a vibrator in the handle 26, or might be someother appropriate warning to the operator. In the event the rate isdetected as being so slow (or even no movement at all) as to present apotential danger of injury to the patient, controls 34 might alsodeactivate source 30 so as to protect the patient.

One problem with radiation treatments is that a significant percentageof the radiation applied to the skin is reflected back or backscatteredby the skin and lost. Various schemes have been proposed in the past forretroreflecting such radiation back into the skin, including for exampleputting some type of reflector in section 50. Sections 52 and 54 mightalso have a reflective coating on their skin contacting surfaces toreflect such radiation back into the skin. Section 72 is particularlyuseful for this purpose since the entire skin-contacting surface 80 ofthis section may be formed of highly reflective material, or have ahighly reflective coating formed thereon. By redirecting most of theradiation back into the skin, the intensity of radiation inside the skincan be increased 1.2 to 2.5 times.

FIG. 5 shows a head 24D an embodiment of the invention which differsfrom that shown in FIG. 4 only in that there is a recessed channel 84formed in skin-contacting surface 80 of section 72, and that opticalchannels 76 a and 76 b terminate on opposite sides of channel 84, withtheir focal point being at a point in the recess, for example at thesubstantial center thereof. A hose 86 is connected at one end to the topof channel 84 and at the other end to a source of negative pressure. Ashead 24D moves in direction 28 across the patient's skin, folds of thepatient's skin are drawn into channel 84. The size of channel 84 isselected such that the target is included in the fold of skin drawn intochannel 84 and is irradiated from both sides by radiation applied tooptical channels 76. For example, if head 24D is being used for hairremoval, channel 84 might be 1 to 6 millimeters wide and 1 to 6millimeters deep, a size which would generally result in the fold havingonly a single hair follicle in the plane shown in the figure, althoughmultiple hair follicles may be in the channel along its long dimension.The configuration of FIG. 5 has several advantages. First, it reducesthe distance for radiation to reach the target and more effectivelyfocuses radiation on the target. Second, if the channel is formed of anoptically reflective material, the walls of channel 84 reflectsubstantially all of the radiation leaving the skin back into the fold,providing for very efficient irradiation.

While in FIG. 5 it is assumed that a line connected to a vacuum or othersource of negative pressure is utilized to draw a fold of skin intochannel 84, a bellows or other suitable mechanism could also be utilizedfor drawing the skin into channel 84 or, as shown in FIG. 7, a head 24Ecould be provided having a channel 84′ formed in a body 72′ of a thermalconductive material, which channel is shaped so that a fold of skin 90which includes the target 92 is forced into channel 84′ as head 24E ismoved in direction 28 over the patient's skin. Successive folds of thepatient's skin would be pushed into channel 84′ as the head moves so asto provide substantially uniform irradiation of the skin in treatmentarea 10. Except that a pre-heater section 52 is not included, theembodiment of FIG. 7 would otherwise operate in substantially the sameway as in the embodiment of FIG. 5 and would afford substantially thesame advantages.

FIG. 8 shows a head 24F which differs from those previously described inthat it has four sets of optical channels 76, channel 76 a, 76 b, 76 c,and 76 d, which for this embodiment are merely light paths through atransparent block or air, each of which is fed by a correspondingflexible waveguides 32 a-32 d, respectively. All of the optical channels76 are angled so as to be substantially focused at target depth 92. Body72″ is curved to facilitate the placement of channels 76 and also has areflecting top surface 93. In addition to components previouslymentioned, FIG. 8 also includes a line 94 leading from a thermocouple orother suitable temperature sensor mounted close to surface 80 or insurface 80. Temperature sensor line 94 connects to controls 34 and maybe utilized to control epidermal temperatures or for other suitablepurposes.

FIG. 9 shows still another embodiment of the invention which, aspreviously indicated, utilizes a cylindrical lens 70 having atransparent window 96 against which is mounted a radiation source 98,which may for example be a laser diode bar, a lamp with a reflector, orother radiation source which is small enough to be mounted in thehandpiece. A reflection plate 100 is provided to perform theretroreflection function for back scattering light. FIG. 9 also shows akinematic motion sensor 102 which may either supplement optical motionsensor 73 or may be used in lieu thereof. Kinematic motion sensor 102may for example be a wheel which turns as cylindrical lens 70 is movedover the skin surface to provide a signal to controls 34 indicative ofscan velocity. Temperature control element 56 is shown as being incontact with both lens 70 and reflection plate 100 so as to cool bothelements, thereby providing both pre-cooling of the treatment area andcooling during irradiation. There is preferably a second element 56 onthe opposite side of cylinder 70 in contact with plate 100 on thetrailing side of the lens which is operative both to further cool thelens and to cool reflection plate 100 and the portion thereof trailingthe lens to provide post-cooling. As indicated previously, cylindricallens 70, particularly if it has a relatively small diameter, for exampleof less than 20 mm, is also operative to focus the radiation at target92 and partly compensate the scattering effect of skin. Except asindicated above, the embodiment of FIG. 9 operates substantially thesame as the prior embodiments to provide scanned CW dermatologictreatment. It should also be noted that, while FIG. 9 is the onlyembodiment showing the radiation source 98 located in head 24 as opposedto the radiation being applied to the head from an external source 30through optical leads 32, an external source 30 or an internal source 98for the head is interchangeable for all embodiments, so that any of theprior embodiments may have an internal radiation source 98 in lieu ofthe arrangement shown, and the embodiment of FIG. 9 may have an externalradiation source with optical leads 32 impinging on transparent window96. For an embodiment such as that shown in FIG. 8, a separate laserdiode bar or bars 98 might for example be provided for each of theoptical channels 76 a-76 d.

FIGS. 10A and 10B show still another handpiece 24H suitable forpracticing the teachings of the invention. This handpiece differs fromthose previously shown in that rather than radiant energy being applieddirectly to the optical waveguide, lens or other transparent componentthrough which radiant energy is applied to the patient's skin, opticallines 32 terminate in a cavity 106 formed in a body 108 of copper or ofsome other material having good thermal conduction properties. The wallsof chamber 106 are polished, coated or otherwise treated to have highlyreflective, and preferably totally reflective, surfaces. The advantageof the configuration shown in FIG. 10 with chamber 106 is that radiantenergy enters cylindrical lens or astigmatic microobjective 70′ at avariety of angles which can be focused by the lens/microobjective to thedesired depth in the skin, the focusing action being more efficient whenthe light enters the lens at a variety of angles than at a single angle.Cylindrical lens 70′ may be mounted in body 108 either rigidly, as forthe embodiment of FIG. 9, or may be mounted for rotation in the body.Rotation of the lens facilitates movement of the head over the patient'sskin, but prevents the desired stretching of the skin. However, arotating lens is within the contemplation of the invention. Thermalelements 56 cool body 102, resulting in both pre-heating, cooling andpost-cooling of the epidermis and also resulting in the cooling ofcylindrical lens 70′ which cools the epidermis during irradiation. Body108 a has reflective skin-contacting surfaces 80 to retroreflect backscattering light from the patient's skin. FIG. 10 also illustrateskinematic motion sensor 102 and a thermocouple or other suitabletemperature sensor 94. Except for the differences discussed above, theembodiment of FIG. 10 functions substantially the same as theembodiments previously discussed.

FIGS. 11 a-11 c illustrate still another embodiment 241 for the head.With this embodiment, cylindrical lens 112, which for example is formedof sapphire, is treated to normally have total internal reflection sothat light or other radiation entering the lens through optical line 32is reflected through the lens and exits through optical lines 32′.However, when lens 112 is in contact with the patient's skin as shown inFIG. 11 c, the total internal reflection at the skin-contacting surfaceis broken due to the change of index of refraction at this surface sothat light energy is emitted from the lens into the patient's skin. Theuse of the total internal reflection lens 112 of FIG. 11 is a safetyfeature which assures that radiation is not applied to a patient orother person unless handpiece 24 is in contact with a patient's skin inthe area to be treated. Except for this difference, the embodiment ofFIG. 11 functions in the manner described for previous embodiments andcomponents such as a housing for pre- and post-cooling, a chiller forthe lens, motion sensors, etc. of prior embodiments might also be usedwith this embodiment.

While for the embodiments of the invention described so far radiationenergy is applied in parallel along the length of the head duringirradiation, FIGS. 12 a and 12 b illustrate embodiments of the inventionwhere light is rapidly scanned. In FIG. 12 a, radiant energy applied tothe head over a line 32 impinges on a deflector 120 which is oscillatedat a rate such that the impinging radiation is scanned in the directionindicated by arrows 122 at the rate previously indicated across acylindrical lens 70″. In FIG. 12 b, the impinging radiation 32 is alsoapplied to an oscillating deflector 120 which scans the beam intooptical fibers 124. Each optical fiber terminates in a microlens 126mounted in a plate 128 of a highly thermal conductive material. Plate128 also preferably has a highly reflective skin-contacting surface 80.So long as the scan rate of deflector 120 is high enough, the radiationoutputted from cylindrical lens 70″ or microlenses 126 is CW radiationas this term has been previously defined, and this system

operates substantially the same as for previous embodiments. Again, forpurposes of simplifying the drawings, elements such as thermal elements56, motion sensor 78 and 102, and temperature sensors 94, are not shownin FIGS. 12 a and 12 b.

FIG. 13 is included to illustrate that pre-heating of the treatmentarea, while more easily facilitated with the CW embodiments heretoforedescribed, is not limited to such embodiments and may be utilized with astandard pulsed head of a type used in some prior art systems. In FIG.13, radiation, which may be pulsed radiation from a source 30, isapplied trough optical lead 32 to an optical waveguide 50 having thermalelements 56 in contact therewith. Waveguide 50, having a focusingskin-contacting end 132, is mounted in a suitable housing, a portion 130of which is shown in the figure. Thermal elements 56, which arethermoelectric elements, for the embodiment shown, but may be other typeof cooling, may be operated to heat waveguide 50 for a time intervalsufficient to heat the skin to the depth z of the target. Either thesame or a different set of thermoelectric elements 56 may then beoperated to cool waveguide 56 for a duration sufficient to coolepidermis 12 to the DE junction 16, at which time source 30 is energizedto apply radiation through waveguide 50 to the target. Cooling ofwaveguide 50 continues during this period to maintain the epidermis at adesired temperature during irradiation and the cooling of waveguide 50may be contained for some period of time after irradiation terminates tofurther protect the patient's skin. Further, while preheating has beenshown and described above followed by epidermal cooling, and for manyapplications this is clearly preferable, it is also within thecontemplation of the invention to do preheating without subsequentcooling. Head designs such as those shown in FIGS. 2, 4, and 5 (eitherwith or without portion 52, and generally without), 8-12, might also beused when operating in a pulsed mode. Operation with these heads in apulsed mode could be similar to operation in a CW mode except thatmovement of the head would be stepped rather than continuous.

While a number of embodiments and variations thereon have been describedabove, it is apparent that these embodiments are for purposes ofillustration only and that numerous other variations are possible whilepracticing the teachings of this invention. For example, while in thediscussion above it has been assumed that head 24 is manually moved overthe treatment area, this is not a limitation on the invention andvarious types of mechanical scanners could also be utilized, eitheralone or in conjunction with manual control. Further, while optical andkinematic movement measuring mechanisms have been shown, suitablethermal, electronic and magnetic

movement measure mechanisms could also be used. Controls 34 wouldfunction to maintain the required scan velocity for such scanner. Thus,while the invention has been particularly shown and described above withreference to preferred embodiments, the foregoing and other changes inform and detail may be made therein by one skilled in the art withoutdeparting from the spirit and scope of the invention which is to bedefined only by the appended claims.

1. A photocosmetic device comprising: a head adapted for applyingradiation to skin, the head comprising a scanner configured to scanradiation in a direction substantially perpendicular to a direction ofmovement of the head as it is moved over the skin, a motion sensorcoupled to the head and adapted to generate one or more signalsindicative of a rate of movement of the head as it is moved over theskin, and controls coupled to the head for receiving said one or moresignals and for controlling the rate of scanning in response to said oneor more signals.
 2. The photocosmetic device of claim 1, wherein thedevice further comprises an alert mechanism configured to provide analert to an operator regarding the rate of head movement over the skin.3. The photocosmetic device of claim 2, wherein the alert mechanism isfurther configured to alert the operator of said device if thedetermined rate of movement is outside of a particular range of rates.4. The photocosmetic device of claim 3, wherein the alert mechanismcomprises at least one of an audio output device, a visual outputdevice, and a tactile output device.
 5. The photocosmetic device ofclaim 1, wherein the motion sensor further comprises a mechanismconfigured to determine the rate of movement of the head over the skin.6. The photocosmetic device of claim 5, wherein the mechanism is furtherconfigured to determine if the head is moving at a rate within apredetermined range of rates, and to provide a further signal to thecontrols based on said determination of the rate of movement.
 7. Thephotocosmetic device of claim 1, wherein the controls are configured toadjust the output of the device if the rate is outside a predeterminedrange of rates.
 8. The photocosmetic device of claim 1, wherein thecontrols are configured to terminate application of the radiation if therate is outside a predetermined range of rates.
 9. The photocosmeticdevice of claim 1, wherein the motion sensor is selected from the groupof a kinematic motion sensor, an optical motion sensor, an electricalmotion sensor, a thermal motion sensor, and a magnetic motion sensor.10. The photocosmetic device of claim 1, wherein the head is configuredto apply continuous wave radiation.
 11. The photocosmetic device ofclaim 1, wherein the scanner comprises an oscillated deflector.